1. Field of the Invention
This invention relates to an electrical current surge suppressor to protect an electrical system, and is particularly, but not exclusively, applicable to automotive electrical systems.
The automotive manufacturer has not until recently been greatly concerned about the problem of transient power surges. Most switching was done by mechanical means such as switches or relays, so that devices not in operation were isolated from surges or they were designed to withstand them.
With recent advances in technology, manufacturers have seen applications for low power complex devices which are very sensitive to transients of the type encountered in an automotive system where switching of heavy inductive loads such as headlights, air-conditioner, window, lights, etc., occurs frequently. These low power devices must be protected from transients so that damage is not done.
2. Prior Art Statement
Transient suppression has, up to now, been handled by self-switching devices, or devices requiring an external signal to switch. Most of these devices are commonly referred to as "crowbar" devices, and operate by either removing all current from or shunting around a load. To restore current, manual action such as resetting a circuit breaker or pressing a reset switch, is usually required. A recent development has been the "Varistor" a semiconductor device which is self-switching, and recovers once current has returned to a normal level for the application. However, the "crowbar" devices allow voltage across a system or device to approach zero, interrupting system or device operation.
The present invention approaches the problem of transients with a goal of non-interference with system operation, while retaining the ability to contain transients so that they are no longer hazards to be reckoned with.